parsers should use strtod() instead of atof() to be able to detect errors

fractint .gif parser doesn't read extended precision metadata

Other

if image is 100% interior, it will never finish rendering. possible algorithm to check this case before starting rendering:

first exclude problematic corner points

boundary points exactly representable as binary floating point

perhaps just exclude real axis and +/- i, are there others?

maybe perturb points if this is the case (make rectangle 0.5px smaller?)

for each corner, check if it is interior

if all corners are interior to the same component

if shape estimate of component is cardioid (non-convex)

(*) calculate interior distance estimates for each point

if there are any regions not excluded by the distance estimates

compute the interior|exterior distance estimate for a point in the middle of such a regions

if interior and same component, exclude another region and goto (*)

otherwise rectangle has exterior points and it's safe to render

else rectangle is 100% interior to a convex circular bulb might be easier to check a region in a previous frame, at least for --interactive and --zoom. for --tile perhaps render a small preview of the view to check interior tiles. --timeout mitigates the problem somewhat.

render.c has a hardcoded maximum period (100000) for finding the first reference

render.c has a hardcoded maximum pass count (1000) for number of references